THURSDAY, Dec. 7, 2017 (HealthDay News) -- When parents bring a premature baby home from the hospital, it's the dads who feel the most stress, a new study finds.

"Dad goes from a situation where the baby and mom are cared for by experts in the hospital to having to simultaneously care for his baby, partner and work. He is supposed to be the 'rock' for his partner but the stress can really set in," said study lead author Dr. Craig Garfield.

He's an associate professor of pediatrics at Northwestern University's Feinberg School of Medicine in Chicago.

"One day of being stressed at home is not a big deal," Garfield said in a university news release. But if a dad's stress levels are still high after two weeks, that's more concerning, he added.

In the study of 86 parents, researchers found that both mothers and fathers of premature babies had high levels of the stress hormone cortisol in their saliva while their infant was in the hospital's neonatal intensive care unit (NICU).

But during the baby's first 14 days at home, mothers' cortisol levels stayed stable while fathers' levels increased.

Also, fathers' cortisol levels indicated a higher level of stress than they reported they felt, the researchers found. That could indicate that they weren't in touch with how stressed they actually were, Garfield said.

The take-home message here? More emphasis should be placed on making fathers of premature babies comfortable and confident with their child while still in the hospital. Relaxation is also important, Garfield added.

"Dads should be telling the mom to go take a walk, take a shower, see a friend," Garfield said. "But moms can also say, 'Why don't you go to the gym, see your friends, meet someone after work?' as ways to reduce some of the stress."

Babies thrive when parents thrive, he added.

"If parents are stressed out, that can impact their parenting of the child, the relationship between the mom and dad and can alter infant attachment," Garfield said. "This all is just much more pronounced with medically vulnerable babies leaving the NICU and going home with mom and dad."

The study was published Dec. 1 in the Journal of Perinatal and Neonatal Nursing.